docs: def disk_param(name, size, snapshot_profile, cmdline=None, kernel=None):
          """ Return disk parameter structure. """
          disk_params = {}
  
          if cmdline:
              disk_params['cmdline'] = cmdline
  
          if kernel:
              disk_params['kernel'] = kernel
  
          if name:
              disk_params['name'] = name
  
          if snapshot_profile is not None:
              disk_params['snapshot_profile'] = snapshot_profile
  
          if size:
              disk_params['size'] = size
  
          return disk_params